In many situations it becomes extremely important, sometimes lifesaving, to have available information regarding the individual's position in space. Typically in such circumstances visual signals are provided to the individual which must be interpreted and, if required, appropriate action taken. Specific examples of such situations are operation of an aerospace vehicle, an individual in outer space such as an operator of a manned maneuvering unit, or a diver, such as a deep sea or scuba diver.
It has been the experience of those skilled in the art that when an individual is under extreme stress the visual signals provided are not always seen and when seen are not always interpreted correctly so that the proper action or reaction is taken. When the proper action or reaction is not taken or conversely if the wrong action results from the visual stimulus, disasterous results, including death or destruction of the vehicle can occur.
It has been found that the application of sound to the human being may, in many instances, obtain the attention of the individual even when a visual stimulus will not do so. Attempts to use sound for such purposes are shown in U.S. Pat. Nos. 2,611,810, 3,089,119 and 3,924,262. The systems disclosed assist the operator but in many instances require further interpretation and may confuse more than aid. This is particularly true because the sound is monaural and requires mental processing before decisions can be made and, furthermore, under stress may be easily ignored. To overcome the monaural sound problem attempts have been made to simulate the binaural hearing of an individual, particularly as an aid for blind persons. Such systems, are exemplified by U.S. Pat. Nos. 3,172,075 and 3,366,922. These systems are, however, used to provide range and azimuth information to the user by receiving reflections of previously transmitted acoustic wave energy returned by objects in the blind person's path.
Human beings experience their aural environment in three dimensions, that is, sound made by objects changes tone and intensity as it moves relative to the listener just as a visually perceived object changes in perspective. Thus, through application of a fully three-dimensional aural environment to the individual, the individual may be able to perceive an indication of his attitude with respect to some predetermined norm and, as a result of such unambiguous three-dimensional aural attitude information, be capable of achieving the desired attitude, whether it be a return to the norm or translation to some predetermined desired position.
The aural norm or "level attitude" may be a prerecorded or artificially generated three-dimensional aural signal. This level attitude aural signal may then be rotated by mathematical or electromechanical transformation so as to indicate to the individual any deviation from the level attitude. The amount of rotation which occurs will be proportional to the individual's deviation from the predetermined level attitude.